A novel low-profile shape memory alloy torsional actuator

• Published in: Smart materials and structures 2010-12, Vol.19 (12), p.125014-125014
• Main Authors: Paik, Jamie K, Hawkes, Elliot, Wood, Robert J
• Format: Article
• Language: English
• Subjects: Actuator materials; Actuators; Density; Exact sciences and technology; General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Joule heating; Physics; Response time; Robots; Shape memory alloys; Strain; Transducers
• ISSN: 0964-1726; 1361-665X
• DOI: 10.1088/0964-1726/19/12/125014

This paper presents low-profile torsional actuators applicable for mesoscale and microscale robots. The primary actuator material is thermally activated Ni--Ti shape memory alloy (SMA), which exhibits remarkably high torque density. Despite the advantages of SMAs for actuator applications--high strain, silent operation, and mechanical simplicity--the response time and energy efficiency limit overall performance. As an alternative to SMA wires, thin SMA sheets are used to fabricate effective yet compact torsional actuators. Also, instead of using conventional Joule heating, an external Ni--Cr heating element is utilized to focus heat on the regions of highest required strain. Various design parameters and fabrication variants are described and experimentally explored in actuator prototypes. Controlled current profiles and discrete heating produces a 20% faster response time with 40% less power consumption as compared to Joule heating in a low-profile (sub-millimeter) torsional actuator capable of 180 degree motion.